Variable delivery gear pump



Oct. 24, 1950 H. M. PURCELL. 2,526,830

VARIABLE DELIVERY GEAR PUMP Filed June 22, 1945 4 Sheets-Sheet 1 I54- 1 V/////////////%///%////%Wy) luvsunm Howmzo M. PuRceLL m M Anew" Oct 24, 1950 H. M. PURCELL.

VARIABLE DELIVERY GEAR PUMP 4 Sheets-Sheet 2 Filed June 22, 1945 QI dz N R 0 T T r A fN ENTOR Q wowm MPumLL Oct. 24, 1950 H. M. PURCELL VARIABLE DELIVERY GEAR mm? 4 Sheets-Sheet 3 L L Nu m& T U w ,0 W 7 W M m w o N Filed June 22, 1945 W RNEYS ATTO Oct. 24, 1950 H. M. PURCELL VARIABLE DELIVERY GEAR PUMP 4 Sheets-Sheet 4 Filed June 22, 1945 NVENTOR Howaao M. PURLELL ATTORNEYS .is a variable speed drive.

Patented a. 24, 1950 VARIABLE DELIVERY GEAR PUMP Howard M. Purcell, Mount Gilead, Ohio, assignor to H-P-M Development Corporation, Wilmington, Del., a corporation of Delaware Application June 22, 1945, Serial No. 606,890

3 Claims.

This invention relates to fluid pumps and, particularly to gear pumps.

The usual type gear pump comprises a, pair 01' pumping gears which run together in mesh within a pump casing which has an inlet port and an outlet port. The gears transfer fluid from the inlet port to the outlet port at a substantially constant rate of flow. If the entire discharge from the pump is not used it must be discharged through a bleed of! valve or through a relief valve to exhaust. This is wasteful of power and is disadvantageous in that it heats the oil and also in that it permits the pump discharge pressure to vary.

In the usual type gear pump the only means vided which is reversible as well as being variable delivery.

It is, therefore, still another object to provide a variable delivery gear pump comprising a plurality 01' pumping gears which are axially slidable relative to one another thereby to vary the rate and direction of delivery from the said pump.

These and other objects and advantages of this invention will become more apparent upon reference to the accompanying specification and v drawings in which:

available for varying the rate of discharge thereof Such a drive is inconvenient and expensive and is not well adapted for mounting in a machine base or in other locations where pumps are usually located.

Accordingly, it is a primary object of the present invention to provide a gear pump having means for varying the discharge rate thereof.

It is another object to provide a gear pump having a substantially constant discharge pressure.

It is still another object to provide a gear pump which is driven from a constant speed source of power and which has a variable rate of discharge.

In a simple two gear pump the only way of reversing the direction of discharge is to reverse the direction of rotation of the pumping gears. This involves the use of a reversible motor or of a reversible transmission.

Accordingly, it is still another object of this invention to provide a gear pump which may be reversed.

It is another object to provide a reversible, variable delivery gear pump which is driven from a substantially constant speed source of power.

The objects of this invention are carried out in general by providing one or more gears in a gear pump which are adapted axially to slide thereby to vary the degree of mesh thereof with another or other pumping gears. Means may be provided for positioning the gears in any degree of mesh thereby to adjust the rate of discharge of the pump and other means may be provided whereby the gears may shift into or out of mesh in response to the discharge pressure of the pump thereby providing for a pressure limiting or pressure holding feature.

By providing a pair of sliding gears in mesh with a driven gear, a gear pump may be pro- Figure '2 is a transverse section on the line 2-2 of Figure 1;

Figure 3 is a section taken on the line 3-3 of Figure 4;

Figure 4 is a section taken on the line 4 l of Figure 3 and illustrates one type of three gear variable delivery gear pump;

Figure 5 is a section indicated on the line 5-5 on Figures 3 and 4;

Figure 6 is a section indicated on the line 6-6 of Figure 3;

Figure '7 is a vertical section through a three gear pump constructed somewhat differently than the pumps of Figures 3 to 6 inclusive;

Figure 8 is a section taken on the line 8-8 of Figure '7; and

Figure 9 is a simplified view showing an arrangement employing four pumping gears.

Referring to the drawings, particularly Figures 1 and 2, I0 indicates a pump casing comprising the central block I2 which is apertured for receiving the pumping gears I4 and I6, and to which are secured end plates I8 and -20. The plates I8 and 20 are bored for receiving the bearings 22 which rotatably support the gear I4 and the plate I8 is further bored for receiving the drive shaft 24 through which power is transmitted to the pumping gears. An oil seal 26 fits around the shaft 24 and prevents the leakage of fluid from within the pump casing.

The pumping gear I6 is rotatably supported on a shaft 28 which terminates at its right end in a threaded portion which receives the nut 30. The shaft 28 is integral with a block 32 which fits against the left face of the gear I6. The nut 30 fits within an aperture 34 in the casing portion 20 and is engaged by a spring 36 which thrusts leftwardly against the nut and gear. The thrust of the spring 36 is adjustable by means of a screw and lock nut arrangement at 38 which 3 passes through the cap 40 secured to the plate of the casing l0.

The block 02, more particularly seen in Figure 2. comprises a key way adapted for engagement with a key 42 carried in the plate l0 of the housing and further comprises an arcuate notch at 44 which is closed by a depending and similarly shaped projection 40 on the plate I0. The notch 44 is shaped exactly to receive the periphery of the gear I4 as the gear I6 is axially shifted relative thereto. The block also comprises the arcuate notch 00 which is connected by the bore 05 with the pumping zone of the gears whereby the gear I6 and block 02 are partially hydraulically I balanced to facilitate their shifting.

The block 32 is abutted by or has integral therewith a piston portion 48 which extends into a bore 50 in the plate I8. A screw 52 which has lock nuts thereon is threaded through the wall of the plate I8 in order adjustably to abut the piston portion 48 thereby to vary the relative position of the gears I4 and I6. The bore 50 is connected by a channel 54 with the outlet port indicated at 55 of the pump. Thus, in response to a predetermined pressure at the discharge port 56, the piston 48 is operable to move the gear I6 transversely of the gear I4 thereby to vary the degree of mesh thereof and thus to vary the pump discharge rate.

The nut 30 is adapted for abutment with the cap 40 at a point which maintains the gears I4 and I0 partially in mesh. This is for the purpose of insuring that the gear I0 will return under the influence of the spring 30 when the opposed thrust thereon is released.

It will be apparent that the capacity of the pump of Figure 1 cannot be reduced to zero because of the minimum amount of mesh of the pumping gears but the said minimum amount ofmesh may be adjusted until the quantity of fluid pumped is only suflicient to make up for leakage within the pump and in the device to which the pump is supplying fluid.

Referring to Figures 3 and 6 inclusive, there is illustrated a pump comprising a casing generally indicated at 60 which includes an inlet 02 and an outlet 64 and within which are rotatably mounted three pumping gears numbered 00, 00 and 10. The gear 66 has connected therewith the drive shaft 12 and is mounted in anti-friction bearings suitably supported within the pump casing 00. The gear 68 is carried on or has integral therewith a shaft l4 and is adapted for continuously meshing with the driven gear 60.

The gear 70 is the sliding gear and is rotatably mounted on a shaft 16 which is integral with a block 18. The end of the shaft 16 is threaded for receiving a nut 80 which retains the gear'in position against the block 18. The shaft 16 is bored from the end thereof as at 82 for receiving the plunger '84 which is adapted for abutment with a screw 86 extending through the cap 88 and being locked in position by the lock nuts 00.

The block 78, similarly as the block 32 in Figures 1 and 2, is provided with an arcuate notch 92 adapted for receiving the periphery of the gear 66 as the gear 10 is adjusted axially relative thereto. Also, similarly to the block 32, the block 18 is provided with the transverse bore 94 which communicates with the segmental area 90 and with the pressure port of the pump thereby at least partially hydraulically to balance the block 18 so that the shifting of the gear I0 may be more easily accomplished. The bore 94 communicates by means of a bore 98 with the cylinder 82 1'01 t e purpose of shifting the gear 10 in response to pump pressure as will hereinafter be described.

Referring to Figure 5 the means for shifting the gear 10 are more particularly shown. There is provided within the pump casing a pivoted lever I00 which beans at one end against the block 18 and, at its other end, against a spring I02, the thrust of which is adjustable by means of a nut and screw arrangement at I04. The arm I00 is divided in approximately the ratio of 1 to 2 so that the movement of the spring is about one half the movement of the gear 10. This permits a shorter, stiffer spring to be employed than could be used if the gear I0 directly engaged the said spring.

The operation of the pump will be evident upon reference to Figures 4 and 6. Assuming that the gears are fully meshed and that the gear 00 is being driven in the direction indicated by the arrow in Figure 4, the gear 68 is transferring fluid away from the inlet passage at I06 while the gear 10 is transferring fluid from the pressure discharge passage I00. The gear 60 is transferring fluid from the discharge e I00 to the discharge I I0 so that the total result of the three gears fully meshed is merely a transfer of fluid within the pump and no transfer of fluid from the inlet port 02 to the discharge port 04.

It, now, the gear 10 is moved partially out oi. mesh with the gear 00, the gears 08 and 00 deliver at full capacity to the discharge port 0 while the gears 60 and I0 withdraw at partial capacity from the discharge port I00. The rwult is a discharge from the discharge port 04 at a rate which is the difference of the aforementioned pumping rates. It will be apparent that the discharge rate of the pump is in inverse ratio to the degree of mesh of the gears 00 and 10.

The spring I02 normally urges the gear II to a position where it is substantially out of mesh with the gear 00. Hence, as the pressure at the discharge port of the pump builds up, the pressure is conducted through the es 04 and 00 to the cylinder 02 where it bears against the piston 04 and urges the gear 10 into a position of greater degree of mesh with the gear 00. The pump is thus adapted for pressure holding or pressure limiting. The screw at 00 provides a mean whereby the capacity of the pump may be varied independently of its pressure characteristics while the screw at I 04 provides means for adjusting the maximum discharge pressure of the pump.

In Figure '7 there is illustrated a modifled arrangement employing the three gears III, 2 and N4 of which the first is the driven gear and the latter two are both slidable. Inasmuch as the mechanism associated with the sliding gears is similar to that shown in Figures 1 to 6, no particular description thereof will be given in connection with Figure 7.

In Figure 8 there is illustrated the condition which prevails when the three gears are fully in mesh. With the gears fully in mesh and rotating in a direction of the arrows, the gears III and I I2 are displacing fluid from the port H0 to the port II8 while the gears H0 and H4 are displacing an equal amount of fluid in the opposite direction. The total result of this exchange 0! fluid is to transfer fluid within the pump and not from one of the ports I I6, I I0 to the other.

If, however, one of the gears I I! or 4 is moved at least partially out of mesh with the gear I I 0, the result will be to discharge fluid from one oi. the ports H6 or H0. Ifthe othergearis moved partially out of mesh the opposite rmult obtain so that complete reversal of the flow from the pump may be had by selectively shifting one or the other of the gears I I2, I ll out of mesh with the gear I III.

The shifting of the gears H2, H4 may be accomplished by means of the screws I20, I22 which thread through the side wall of the pum casing I24. The gear which remains in mesh with the gear IIO may be provided with a plunger such as those indicated at I26 and I in association with the gears H2. and Ill respectively, which is connected with the discharge ports of the pump so that at a predetermined discharge pressure the gear will be shifted out of mesh with the gear IIO thereby providing for a pressure holding or a pressure limiting feature. Optionally, the gear which is out of mesh with the gear IIO may be similarly shifted into mesh under pressure thereby to reduce or to limit the pump discharge. As indicated in Figure 8, the plunger I26 of the gear II2 may be connected by a passage I30 with the discharge port II8 while the plunger I28 of the gear III may be connected by the passage I32 with the discharge port II 6.

There is illustrated in Figure 9 still another arrangement for obtaining a reversible variable delivery pump, this modification employing four gears rather than three. In Figure 9 the gear I and the gear I52 rotates in mesh continuously within the pump casing I54. There is provided also the gear 556 which meshes with the gear I50 and which is mounted on trunnions so as to be axially slidable similarly as the sliding gears in the previous figures. A fourth gear I58 is also trunnion mounted and is axially shiftable in mesh with the gear I52. The pump casing I54 comprises thepassageways or ports I and I62 which communicate with the pumping zones of the gears.

When the gears are' fully in mesh and are being rotated in the direction indicated by the arrows they are transferring fluid from the port I60 to the port I62. When the slidable gears I56 and I50 are half meshed with their associated gears I50 and I52 there is no transfer of fluid between the ports I 60 and I62. When the slidin gears are substantially out of mesh, the transfer'of fluid is from the port I62 to the port I60.

The gears I56 and I58 may be mechanically moved in either direction so as to select the direction of delivery of the pump and may further be provided with yielding means and fluid pressure I responsive means properly connected with the ports I50 and I62 so the pump will hold or limit pressure in either direction of delivery thereof.

While no means for balancing the gears have been shown, it will be understood that any well known arrangement for hydraulically balancing the said gears could be used in order to increase the available discharge pressure and to give better operating efllciency.

It will be understood that various modifications and arrangements in structure could be made without departing from the spirit of my invention and, accordingh'. I desire to comprehend such modifications and substitutions of equivalents as may be considered to come within the scope of 1 the appended claims.

III

within said casing for rotation and for relative axial sliding movement with respect to said first gear for varying the degree of mesh thereof with said first gear; a first passageway in said casin communicating with the outlet port thereof and disposed adjacent the meshing portions of said first and second gears to receive fluid circulated by said first and second gears; a second passageway in said casing communicating with the outlet port thereof and disposed adjacent the meshing portions of said first and third gears to supply fluid for circulation by said first and third gears when the latter is fully meshed with said first gear and to receive fluid circulated by said first gear when said third gear occupies a position other than a position of full mesh with respect to said first gear, spring and levermeans to urge said third gear to a position of minimum mesh with respect to said first gear; and means responsive to a predetermined pressure at the outlet port of said casing to move said third gear toward a position of full mesh with respect to said first gear.

2. In a gear pump having a casin formed with a fluid inlet, a fluid outlet, and an internal gear chamber communicating with the fluid inlet by way of a single passage and with the fluid outlet by way of a pair of separate passages; a first driving gear rotatably mounted within the gear chamber of said casing between the two passages communicating with the fluid outlet of the casing; a second pumping gear rotatably mounted within the gear chamber of said casing adjacent one of the passages communicating with the fluid outlet and in mesh with said first drivin gear, said second pumping gear being operable upon rotation of said first driving gear to circulate fluid between the fluid inlet and one of the passages communicating with the fluid outlet: and a third pumpin gear in mesh with said first driving gear and mounted within said casing adjacent .the other passage communicating with the fluid outlet thereof for rotational and relative axial sliding movement with respect to said first driving gear whereby to vary the degree of mesh thereof with said first driving gear, said third gear being operable upon rotation of said first gear and when fully meshed therewith to circulate fluid between the last-named passage communicating with the fluid outlet and the fluid inlet of said casing and when substantially out of mesh with said first gear to permit the latter to circulate fluid between the fluid inlet and, the last-named passage of said casing.

3. In a gear pump; a casing formed with a fluid I inlet, a fluid outlet, a pumping chamber, a single passageway connecting the fluid inlet with the pumping chamber at one end thereof, and a pair of relatively spaced separate passageways connecting the fluid outlet with the pumping chamber at its opposite end; a first driven pumping gear rotatably mounted within the pumping chamber of said casing between the pair of passageways communicating with the fluid outlet; a second pumping gear rotatably carried within the pumping chamber of said casing in mesh with said first pumping gear and disposed adjacent one of the pair of passageways communicating with the fluid outlet of said casing, said second gear being operable upon rotation of said first gear to circulate fluid from the passageway communicating with the fluid inlet to the passageway adjacent thereto communicating with the fluid outlet of said casing; and'a third pump-' ing gear in mesh with said first gear mounted 7 within said casing for rotational andaxial sliding movement with respect to said first gear whereby to vary the degree of mesh thereof with said flrst gear and disposed adjacent the other of the pair of eways communicating with the fluid outlet of said casing, said third gear when occupying a position of full mesh with said flrst gear and when rotated therby serving to circulate fluid item the passageway adjacent thereto and communicating with the fluid outlet to the passageway communicating with the fluid inlet, and when occupyin a position substantially out of mesh with said flrst gear providing for the circulation of fluid by said first gear from the passageway communicating with the fluid inlet to the passageway adjacent said third gear commlmieating with the fluid outlet of said casing.

HOWARD M. PURCEIL.

REFERENCES mm The following references are of record in the flle of this patent:

UNITED s'ra'rns mmrs Number Name Date 1,879,219 Harbison Sept. 27. 1932 2,079,375 McCollum May 4, 1937 2,157,284 Egersdorfer May 9, 1939 roman m'mu'rs Number coimtry Date 421,868 Great Britain Jan. 1, 1935 

